1. Field of the Invention
This invention relates generally to arrangements and methods for suturing soft tissue to bone, and more particularly, to a system wherein soft tissue is sutured to a suture anchor, and a bone anchor is embedded in a bone, the suture anchor and the bone anchor then being mechanically coupled to one another in a manner whereby the engagement is reversible.
2. Description of the Related Art
The fixation of soft tissue to bone remains a perplexing problem. The physical properties of bone and soft tissue are so different that techniques which provide adequate fixation to bone do not provide adequate fixation to soft tissue. This problem is especially difficult when trying to use arthroscopic or mini incision techniques. The prior art has thrust at this problem with a variety of anchors which can couple suture material to bone. However, no system is known to be available which achieves adequate fixation of the soft tissue to bone.
Rotator cuff avulsions, rotator cuff tears close to the bone, and other soft tissue avulsions and tears are lesions consisting of separations of soft tissue from bone or near bone. A surgeon endeavoring to effect repair must adequately secure the torn soft tissue to the bone utilizing open surgical procedures. However, the repair cannot be achieved using current arthroscopic surgical techniques. The problems associated with known fixation devices, whether used arthroscopically or in standard surgical techniques, can be divided into three separate problems:
(1) soft cancellous bone and very hard cortical bone are not amenable to current surgical soft tissue to bone fixation devices. Known devices are suitable for the fixation of a soft tissue to average bone of average density; PA1 (2) various sizes and configurations are required depending upon the sizes of the soft tissue and bone defects. Known arrangements, however, do not have any flexibility with regard to size or configuration; and PA1 (3) known arrangements do not permit the use of appropriate surgical techniques to maximize the soft tissue to bone fixation, to achieve adequate strength of the fixation. PA1 coupling the soft tissue of the living being to a first coupling portion of a suture anchor; PA1 coupling an external portion of a bone anchor with the bone of the living being; and PA1 engaging a second coupling portion of the suture anchor with an internal portion of the bone anchor.
One known arrangement for use in the fixation of soft tissue to bone employs two to four prongs. The prongs are embedded into the bone after pre-drilling a hole in the bone and preparing the bone surface to accept the soft tissue. The prongs are embedded in cancellous bone which is soft and can yield under stress.
The required preparation of the bone immediately above the device weakens the bone, thereby predisposing the bone to failure. Bone which is very narrow or very hard is difficult to prepare to accept this known device. There is no variation of the device for very soft cancellous bone. One attempt to overcome the difficulties associated with this known device require the use of double rows of the device in order to achieve adequate fixation to soft bone. This procedure is cumbersome and requires a large surgical exposure.
In the use of this known device, the force with which the soft tissue is drawn toward the bone is related to the tension placed on the suture during knot tying. However, when arthroscopic techniques are employed, the tension which is applied by the surgeon during knot tying is variable and inconsistent.
Another problem which is associated with the use of the known device occurs if the suture breaks after the device is embedded into bone. New suture material cannot be threaded through the device. Once the device is embedded in bone, there is no method of removing the device. The only way to salvage a broken suture is to place another device next to the one that has failed. The existence of extra metal embedded in bone is prone to infection. Additionally, the placement of multiple devices next to one another weakens the bone. Of course, since the device cannot easily be removed, its presence will complicate further reconstructive procedures.
Another known device for use in anchoring soft tissue to bone employs screw threads for bone fixation. This known device achieves an advantage over that described hereinabove in that it can be removed if the suture breaks during tightening. However, in all other respects the mechanics of this fixation device are similar to that described above, particularly in regard of tying and tensioning of the suture and soft tissue.
There currently are two absorbable fixation devices on the market. These devices penetrate the tissue directly, but do not use sutures. Tissue is tensioned using instruments while the device is driven through the soft tissue into a pre-drilled bone hole. Once the device is placed, there is no method of salvage. Thus, if the device fails, such as by fracturing, it cannot be removed from the bone.
All of the known devices transmit forces parallel to the direction of penetration into the bone. The pull-out strength of the fixation of the soft tissue to the bone is therefore directly related to the pull-out strength of the bone fixation device. In addition, all of the known devices secure the soft tissue directly to the bone above the fixation device. Any preparation of the bone to allow better healing of soft tissue to the bone weakens the bone in the area of the fixation device.
In addition to the foregoing, all of the known devices ignore the forces of the tendon during active contraction of the muscle attached to the tendon. Tension wire fixation techniques allow contraction of the muscles pulling on the fracture or soft tissue to compress the fractured bone or torn surfaces together, promoting healing. The current devices used to fix soft tissue to bone, allow the forces associated with contraction of the muscle attached to the soft tissue to distract the soft tissue away from the bone, thereby interfering with healing.
Current measurements of the efficacy of the state of the art soft tissue to bone fixation arrangements generally relate to the pull-out strength of the fixation devices or the strength and failure of the fixation to soft tissue. The actual strength of fixation is related to the strength of the entire complex, consisting of the soft tissue fixation, the fixation device, and the underlying bone.
When multiple fixation devices are used, problems with surgical techniques occur. All of the known surgical devices, such as those described herein, require that the device be placed in the bone with its sutures attached. If four such devices are used, eight sutures will be hanging in the surgical field attached to the bone, but not attached to soft tissue. Once the surgeon places the sutures through the tendon, he has no way of applying tension on the sutures to see how well the soft tissue will be fixed to the bone. Once the sutures are placed in the soft tissue, it is difficult to replace them, in the event the placement is incorrect. Additionally, as previously stated, knot tying is difficult when attempting arthroscopic procedures. This compounds the problem of multiple free sutures in the joint.
In cancellous bone, the conventional tacks, screws, and staples do not provide adequate fixation to the bone. The bone is generally very soft and does not hold fixation devices well. There are available cancellous screws for use in fixing soft tissue to cancellous bone. These screws can be fitted with special washers for holding tendons and other soft tissue. The cancellous screws, however, stand proud above the bone and impinge against other bony structures in the joint or against other anatomic structures. Thus, there is a need for an arrangement which achieves a substantially flush fixation with respect to the surface of the bone.
It is, therefore, an object of this invention to provide a simple and economical device which removably fixes soft tissue to bone.
It is another object of this invention to provide an arrangement for anchoring soft tissue to soft cancellous bone, or very hard conical bone.
It is also an object of this invention to provide an arrangement for fixing soft tissue to bone which can be configured in a variety of sizes depending upon the size of the soft tissue and bone defects.
It is a further object of this invention to provide a system and method of tissue to bone fixation which permits proper surgical techniques to be employed to maximize the strength of the tissue to bone fixation.
It is additionally an object of this invention to provide a system of fixing a soft tissue to bone which does not require a large surgical exposure.
It is yet a further object of this invention to provide a system for fixing soft tissue to bone wherein the strength of the fixation does not rely upon the variable and inconsistent tension which is applied by a surgeon during the tying of a knot.
It is also another object of this invention to provide an apparatus and method of fixing soft tissue to bone which does not require the installation of a second bone anchor in the event a suture material breaks.
It is yet an additional object of this invention to provide an arrangement for fixing soft tissue to bone which does not require numerous sutures to hang in the surgical field.
It is still another object of this invention to provide a tissue to bone fixation arrangement which can be installed to be flush with the surface of the bone, or slightly therebelow.